As the examples of laser processing method for making holes, there are a processing method (hereinafter, called “stationary processing”) in which laser scanning is performed on a workpiece mounted on a stationary table, and another processing method (hereinafter, called “synchronization processing”) in which laser scanning is performed on a workpiece mounted on a table while moving the table in order to accelerate the processing speed.
Japanese Patent No. 3561159, Patent Laid-Open No. 2004-142082, and Japanese Patent Laid-Open No. 2012-187620 disclose the inventions related to the synchronization processing. Especially Japanese Patent Laid-Open No. 2004-142082 discloses a processing method in which the stationary processing and the synchronization processing are combined (hereinafter, called “combination processing”). In the combination processing, the synchronization processing is performed when a workpiece has a uniformly low density of holes. When the workpiece has an uneven density of holes, the synchronization processing is performed in areas having low densities of holes and the stationary processing is performed in areas having high densities of holes.
However, in the method disclosed in Japanese Patent Laid-Open No. 2004-142082, the areas having low densities of holes are subjected to the synchronization processing and the table preferably be moved across the areas within the time periods for the laser scanning in the areas as timely as possible. If the density of hole in an area is extremely low, however, it is difficult to move the table within the time period for the laser scanning in the area, which may necessitate a halt in the laser scanning and slow down the overall processing speed. In addition, when the synchronization processing in an area having an extremely low density of holes is followed by the stationary processing, or in the opposite case, the state of the table should be transferred from a high-speed moving state to a stationary state, or in the opposite direction, which increases the change in the speed of the table and makes it difficult to keep the accuracy of finishing. When the stationary processing is performed in an area having a high density of holes, for making processing of the next area, the table should be moved over a long distance in correspondence to the stationary processing. As a result of this, if the processing speed is intended to be accelerated by increasing the speed of the table, it will increase the change in the speed of the table and make it difficult to keep the accuracy of finishing.